1. Field of the Invention
The present invention relates to the field of semiconductor packaging, and, more particularly, to wire bonding of semiconductor packages.
2. Description of Related Art
Wire bonding involves electrical connection of a semiconductor chip and a substrate, such as a printed circuit board (PCB) or a lead frame. Conventionally, an organic solderability preservative (OSP) material is placed on a contact pad so as to prevent surface oxidation of the contact pad. In the typical process, an organic material is formed on the bare contact pad to protect the contact pad from being oxidized. The organic material is removed from the contact pad when access to the contact pad is desired. However, after removing the organic material, the surface of the pad is exposed and may be immediately oxidized as it reacts with outside elements, such as moisture. This may result in poor solderability in subsequent soldering or bonding processing. Alternatively, a conductive nickel-gold layer can be used but the material cost is relatively high because gold is expensive.